Continuous Positive Airways Pressure


Continuous Positive Airways Pressure, CPAP

  • Indications
  1. Obstructive Sleep Apnea
    1. See CPAP for Obstructive Sleep Apnea
  2. Loud continuous snoring
  3. Noninvasive positive airway pressure in respiratory distress (BIPAP offers similar respiratory support)
    1. See Acute Respiratory Failure
    2. Bridge to intubation in severe respiratory illness
    3. Adult Respiratory Distress Syndrome (ARDS)
    4. Refractory Hypoxemia
    5. Respiratory Failure in children and chronic airway disease
  • Contraindications
  • Mechanism
  1. Non-Invasive Positive Pressure Ventilation
    1. Used during spontaneous breathing (as with BIPAP)
  2. Pressure above atmospheric maintained at airway opening
    1. Maintained throughout respiratory cycle
    2. Acts as airway splint to prevent collapse of alveoli and Bronchioles
      1. Also decreases airway resistance by Splinting open inflamed or bronchospastic airways
      2. Overcomes anatomic airway resistance (e.g. Obstructive Sleep Apnea)
    3. Increases surface area for gas exchange
      1. Increases oxygen diffusion and improves Hypoxemia
    4. Decreases work of breathing
      1. Decreases pressure required on inspiration
  3. Same end-expiratory pressure as with PEEP
  4. Lower Inspiratory pressure excursion than with PEEP
    1. CPAP requires less pressure to open
    2. PEEP requires a greater work of breathing
  • Approach
  • Noninvasive positive airway pressure in respiratory distress
  1. See Acute Respiratory Failure
  2. Indications
    1. Hypoxemic Acute Respiratory Failure (inadequate tissue Oxygen Delivery)
      1. Interstitial Lung Disease
      2. Congestive Heart Failure
      3. Pneumonia
    2. Not indicated for hypercarbic Acute Respiratory Failure
      1. CPAP only delivers Oxygen and increased end-expiratory pressure
      2. Only BiPap (increases Tidal Volume) or Mechanical Ventilation can correct Ventilatory failure
  3. Delivery mechanisms
    1. High Flow Nasal Cannula
    2. Face Mask
  4. Technique CPAP Face Mask
    1. Target pressure range: 5-10 mmHg (continuous airway pressure)
      1. Contrast with the bi-level airway pressure of BIPAP (e.g. 15 mmHg inspiratory and 5 mmHg expiratory)
      2. CPAP pressure can be increased up to a maximum of 20 mmHg
        1. Pressure >20 mmHg exceeds lower esophageal sphincter pressure
    2. Start
      1. Set initial cpap pressure to 2-3 cm H2O
      2. Patient self-applies Face Mask
      3. Slowly increase the pressure
  • Adverse Effects
  • Relates to decreased mask tolerance
  1. Nasal dryness or congestion
  2. Mask air leakage
  3. Claustrophobia
  4. Skin irritation or abrasions
  5. Conjunctivitis
  • Efficacy
  • Noninvasive positive airway pressure in respiratory distress
  1. CPAP and BIPAP have similar outcomes in respiratory distress
  2. CPAP may be better tolerated in some cases (no need to synchronize their breaths with different inspiratory and expiratory pressure phases)
  3. Li (2013) Am J Emerg Med 31(9): 1322-7 [PubMed]